A friend has a bonsai apple which is very vigorous, with long shoots. She's thinking of cutting back the long shoots (leaving end leaf to prevent simple extension) and then de-foliating. Will this work for stimulating buds behind? (or will it sulk and not work?!)

A friend has a bonsai apple which is very vigorous, with long shoots. She's thinking of cutting back the long shoots (leaving end leaf to prevent simple extension) and then de-foliating. Will this work for stimulating buds behind? (or will it sulk and not work?!)

To stimulate back budding, one must cause the auxin flow to 'collapse' (i.e., fall dramatically in a short period of time). Hardened foliage and especially the growth tip are the sources of auxin - cut the tip and most of the hardened leaves will cause backbudding.

What your friend is proposing will not cause backbudding. In fact keeping the tip will likely suppress the release of any axilary buds, so there will be few to no new leaves and the tree will appear to just "sulk" (next season the tree will be weaker).

The best thing to do for both a healthy tree and for developing ramification is to let the shoots extend with foliage until its growth rate slows, then cut it back removing nearly all of that long new shoot. In the temperate northern hemisphere, this happens in May (or thereabouts). Then around August you can likely do it again. This should leave any fruit set, but you may need to partially defioliate to keep light getting to those sprigs.

Lastly, you may need to adjust this general approach if you are after flowers/fruit. Next season's flowers are set on this season's new growth IIRC, so you may want to go lightly or even eliminate the pruning ca. August, for example.